1. Field of the Invention
The present invention relates to a developing apparatus for use in an electrophotographic image forming apparatus such as copying machine, laser beam printer, or facsimile, and more particularily to the developing apparatus for providing a photoreceptor with toner particles to develop an electrostatic latent image on the photoreceptor into a visible powder image.
2. Description of Related Art
There has been known a single-magnetic pole type developing apparatus in the art. The developing apparatus comprises a developer roller adjacent to the photoreceptor in order to apply a developer material onto the photoreceptor. The developer roller consists of a non-rotatably supported magnetic member having a plurarity of magnetic poles on its outer periphery with only one of said magnetic poles confronting the photoreceptor, and a rotatably supported sleeve enclosing the magnetic member therein. Developer material of two-component type, which is a mixture of toner particles and carrier particles, is magnetically retained on an outer periphery of the sleeve magnetically by the magnetic member and is transported during a rotation of the sleeve to a developing region where the sleeve confronts the photoreceptor. In the developing region, the developer material retained on the sleeve by the sole magnetic pole confronting the photoreceptor is brought into contact with the photoreceptor for developing the electrostatic latent image into a visible powder image.
However, the developing apparatus of this type has a drawback that the width of contact of the developer material with the photoreceptor with respect to the rotation of the sleeve is not so large that it is difficult to reproduce the electrostatic latent image into a visible powder image of high density.